lwn.git/mm/page-writeback.c, branch v4.14

mm: rename global_page_state to global_zone_page_state

2017-09-07T00:27:29+00:00

global_page_state is error prone as a recent bug report pointed out [1]. It only returns proper values for zone based counters as the enum it gets suggests. We already have global_node_page_state so let's rename global_page_state to global_zone_page_state to be more explicit here. All existing users seems to be correct: $ git grep "global_page_state(NR_" | sed 's@.*($NR_[A-Z_]*$).*@\1@' | sort | uniq -c 2 NR_BOUNCE 2 NR_FREE_CMA_PAGES 11 NR_FREE_PAGES 1 NR_KERNEL_STACK_KB 1 NR_MLOCK 2 NR_PAGETABLE This patch shouldn't introduce any functional change. [1] http://lkml.kernel.org/r/201707260628.v6Q6SmaS030814@www262.sakura.ne.jp Link: http://lkml.kernel.org/r/20170801134256.5400-2-hannes@cmpxchg.org Signed-off-by: Michal Hocko Signed-off-by: Johannes Weiner Cc: Tetsuo Handa Cc: Josef Bacik Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: memcontrol: fix NULL pointer crash in test_clear_page_writeback()

2017-08-18T22:32:01+00:00

Jaegeuk and Brad report a NULL pointer crash when writeback ending tries to update the memcg stats: BUG: unable to handle kernel NULL pointer dereference at 00000000000003b0 IP: test_clear_page_writeback+0x12e/0x2c0 [...] RIP: 0010:test_clear_page_writeback+0x12e/0x2c0 Call Trace: end_page_writeback+0x47/0x70 f2fs_write_end_io+0x76/0x180 [f2fs] bio_endio+0x9f/0x120 blk_update_request+0xa8/0x2f0 scsi_end_request+0x39/0x1d0 scsi_io_completion+0x211/0x690 scsi_finish_command+0xd9/0x120 scsi_softirq_done+0x127/0x150 __blk_mq_complete_request_remote+0x13/0x20 flush_smp_call_function_queue+0x56/0x110 generic_smp_call_function_single_interrupt+0x13/0x30 smp_call_function_single_interrupt+0x27/0x40 call_function_single_interrupt+0x89/0x90 RIP: 0010:native_safe_halt+0x6/0x10 (gdb) l *(test_clear_page_writeback+0x12e) 0xffffffff811bae3e is in test_clear_page_writeback (./include/linux/memcontrol.h:619). 614 mod_node_page_state(page_pgdat(page), idx, val); 615 if (mem_cgroup_disabled() || !page->mem_cgroup) 616 return; 617 mod_memcg_state(page->mem_cgroup, idx, val); 618 pn = page->mem_cgroup->nodeinfo[page_to_nid(page)]; 619 this_cpu_add(pn->lruvec_stat->count[idx], val); 620 } 621 622 unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order, 623 gfp_t gfp_mask, The issue is that writeback doesn't hold a page reference and the page might get freed after PG_writeback is cleared (and the mapping is unlocked) in test_clear_page_writeback(). The stat functions looking up the page's node or zone are safe, as those attributes are static across allocation and free cycles. But page->mem_cgroup is not, and it will get cleared if we race with truncation or migration. It appears this race window has been around for a while, but less likely to trigger when the memcg stats were updated first thing after PG_writeback is cleared. Recent changes reshuffled this code to update the global node stats before the memcg ones, though, stretching the race window out to an extent where people can reproduce the problem. Update test_clear_page_writeback() to look up and pin page->mem_cgroup before clearing PG_writeback, then not use that pointer afterward. It is a partial revert of 62cccb8c8e7a ("mm: simplify lock_page_memcg()") but leaves the pageref-holding callsites that aren't affected alone. Link: http://lkml.kernel.org/r/20170809183825.GA26387@cmpxchg.org Fixes: 62cccb8c8e7a ("mm: simplify lock_page_memcg()") Signed-off-by: Johannes Weiner Reported-by: Jaegeuk Kim Tested-by: Jaegeuk Kim Reported-by: Bradley Bolen Tested-by: Brad Bolen Cc: Vladimir Davydov Cc: Michal Hocko Cc: [4.6+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

writeback: rework wb_[dec|inc]_stat family of functions

2017-07-12T23:26:05+00:00

Currently the writeback statistics code uses a percpu counters to hold various statistics. Furthermore we have 2 families of functions - those which disable local irq and those which doesn't and whose names begin with double underscore. However, they both end up calling __add_wb_stats which in turn calls percpu_counter_add_batch which is already irq-safe. Exploiting this fact allows to eliminated the __wb_* functions since they don't add any further protection than we already have. Furthermore, refactor the wb_* function to call __add_wb_stat directly without the irq-disabling dance. This will likely result in better runtime of code which deals with modifying the stat counters. While at it also document why percpu_counter_add_batch is in fact preempt and irq-safe since at least 3 people got confused. Link: http://lkml.kernel.org/r/1498029937-27293-1-git-send-email-nborisov@suse.com Signed-off-by: Nikolay Borisov Acked-by: Tejun Heo Reviewed-by: Jan Kara Cc: Josef Bacik Cc: Mel Gorman Cc: Jeff Layton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'for-linus-v4.13-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux

2017-07-08T01:39:15+00:00

Pull Writeback error handling fixes from Jeff Layton: "The main rationale for all of these changes is to tighten up writeback error reporting to userland. There are many ways now that writeback errors can be lost, such that fsync/fdatasync/msync return 0 when writeback actually failed. This pile contains a small set of cleanups and writeback error handling fixes that I was able to break off from the main pile (#2). Two of the patches in this pile are trivial. The exceptions are the patch to fix up error handling in write_one_page, and the patch to make JFS pay attention to write_one_page errors" * tag 'for-linus-v4.13-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux: fs: remove call_fsync helper function mm: clean up error handling in write_one_page JFS: do not ignore return code from write_one_page() mm: drop "wait" parameter from write_one_page()

mm: memcontrol: per-lruvec stats infrastructure

2017-07-06T23:24:35+00:00

lruvecs are at the intersection of the NUMA node and memcg, which is the scope for most paging activity. Introduce a convenient accounting infrastructure that maintains statistics per node, per memcg, and the lruvec itself. Then convert over accounting sites for statistics that are already tracked in both nodes and memcgs and can be easily switched. [hannes@cmpxchg.org: fix crash in the new cgroup stat keeping code] Link: http://lkml.kernel.org/r/20170531171450.GA10481@cmpxchg.org [hannes@cmpxchg.org: don't track uncharged pages at all Link: http://lkml.kernel.org/r/20170605175254.GA8547@cmpxchg.org [hannes@cmpxchg.org: add missing free_percpu()] Link: http://lkml.kernel.org/r/20170605175354.GB8547@cmpxchg.org [linux@roeck-us.net: hexagon: fix build error caused by include file order] Link: http://lkml.kernel.org/r/20170617153721.GA4382@roeck-us.net Link: http://lkml.kernel.org/r/20170530181724.27197-6-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Signed-off-by: Guenter Roeck Acked-by: Vladimir Davydov Cc: Josef Bacik Cc: Michal Hocko Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: clean up error handling in write_one_page

2017-07-05T22:44:22+00:00

Don't try to check PageError since that's potentially racy and not necessarily going to be set after writepage errors out. Instead, check the mapping for an error after writepage returns. That should also help us detect errors that occurred if the VM tried to clean the page earlier due to memory pressure. Signed-off-by: Jeff Layton Reviewed-by: Jan Kara

mm: drop "wait" parameter from write_one_page()

2017-07-05T22:44:22+00:00

The callers all set it to 1. Also, make it clear that this function will not set any sort of AS_* error, and that the caller must do so if necessary. No existing caller uses this on normal files, so none of them need it. Also, add __must_check here since, in general, the callers need to handle an error here in some fashion. Link: http://lkml.kernel.org/r/20170525103303.6524-1-jlayton@redhat.com Signed-off-by: Jeff Layton Reviewed-by: Ross Zwisler Reviewed-by: Jan Kara Reviewed-by: Matthew Wilcox Reviewed-by: Christoph Hellwig Signed-off-by: Andrew Morton

Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

2017-05-08T18:30:05+00:00

Pull ext4 updates from Ted Ts'o: - add GETFSMAP support - some performance improvements for very large file systems and for random write workloads into a preallocated file - bug fixes and cleanups. * tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: jbd2: cleanup write flags handling from jbd2_write_superblock() ext4: mark superblock writes synchronous for nobarrier mounts ext4: inherit encryption xattr before other xattrs ext4: replace BUG_ON with WARN_ONCE in ext4_end_bio() ext4: avoid unnecessary transaction stalls during writeback ext4: preload block group descriptors ext4: make ext4_shutdown() static ext4: support GETFSMAP ioctls vfs: add common GETFSMAP ioctl definitions ext4: evict inline data when writing to memory map ext4: remove ext4_xattr_check_entry() ext4: rename ext4_xattr_check_names() to ext4_xattr_check_entries() ext4: merge ext4_xattr_list() into ext4_listxattr() ext4: constify static data that is never modified ext4: trim return value and 'dir' argument from ext4_insert_dentry() jbd2: fix dbench4 performance regression for 'nobarrier' mounts jbd2: Fix lockdep splat with generic/270 test mm: retry writepages() on ENOMEM when doing an data integrity writeback

mm: memcontrol: use node page state naming scheme for memcg

2017-05-03T22:52:11+00:00

The memory controllers stat function names are awkwardly long and arbitrarily different from the zone and node stat functions. The current interface is named: mem_cgroup_read_stat() mem_cgroup_update_stat() mem_cgroup_inc_stat() mem_cgroup_dec_stat() mem_cgroup_update_page_stat() mem_cgroup_inc_page_stat() mem_cgroup_dec_page_stat() This patch renames it to match the corresponding node stat functions: memcg_page_state() [node_page_state()] mod_memcg_state() [mod_node_state()] inc_memcg_state() [inc_node_state()] dec_memcg_state() [dec_node_state()] mod_memcg_page_state() [mod_node_page_state()] inc_memcg_page_state() [inc_node_page_state()] dec_memcg_page_state() [dec_node_page_state()] Link: http://lkml.kernel.org/r/20170404220148.28338-4-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Acked-by: Vladimir Davydov Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: memcontrol: re-use node VM page state enum

2017-05-03T22:52:11+00:00

The current duplication is a high-maintenance mess, and it's painful to add new items or query memcg state from the rest of the VM. This increases the size of the stat array marginally, but we should aim to track all these stats on a per-cgroup level anyway. Link: http://lkml.kernel.org/r/20170404220148.28338-3-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Acked-by: Vladimir Davydov Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds